1. Field of the Invention
The present invention relates to mobile-service switches, a home memory node, and a gateway switch in a mobile communication system of a small zone scheme. Each mobile-service switch incorporates a plurality of processors that cooperate with each other during the course of call processing on a call that has occurred in an individual mobile station and share predetermined loads and functions. The home memory node provides location information of the mobile stations. The gateway switch cooperates with the mobile-service switches and the home memory node and interfaces with a desired network.
2. Description of the Related Art
In mobile communication systems, load distribution and functional distribution are attained by incorporating, in radio base stations, base station controllers, and switch offices, a number of processors that are inexpensive and superior in performance and cooperate with each other and total reliability and flexible adaptation to a variety of forms relating to expansion, maintenance, and operation are secured.
FIG. 17 shows an example configuration of a mobile communication system to which a distributed processing scheme is applied.
As shown in FIG. 17, a gateway switch office 60 is connected to a mobile-service switch office 70 via inter-office links 61-1 to 61-N and also connected to a home location register 80 via a communication link 62. The home location register 80 is connected to corresponding ports of the mobile-service switch office 70 via communication links 81-1 to 81-N. The mobile-service switch office 70 is connected to radio base stations 90-1 to 90-N via respective sets of digital links 71-1 to 71-1n, . . . , 71-N1 to 71-Nn. A mobile station 92 is located in, for example, a wireless zone 91-3 among wireless zones 91-1 to 91-N that are formed by the respective radio base stations 90-1 to 90-N.
The mobile-service switch office 70 is comprised of the following components (1)-(3):
(1) A main processor (MPR) 72
(2) A communication link 73 connected to the communication port of the main processor 72.
(3) Submodules 74-1 to 74-N that have respective communication ports connected to the main processor 72 via the communication link 73 and that are connected to the respective inter-office links 61-1 to 61-N, the respective communication links 81-1 to 81-N, and the respective sets of digital links 71-11 to 71-1n, . . . , 71-N1 to 71-Nn. 
The submodule 74-1 is composed of the following components (a)-(e):
(a) A switch module 75-1
(b) a call processor (CPR) 76-1 having a port that is connected to the control terminal of the switch module 75-1 and the above-mentioned communication port that is connected to the communication link 73.
(c) A digital trunk (DT) 77G-1 that is directly connected to the inter-office link 61-1 and is connected to one, of the ports of the switch module 75-1, corresponding to the inter-office link 61-1.
(d) A digital trunk (DT) 77H-1 that is directly connected to the communication link 81-1 and is connected to one, of the ports of the switch module 75-1, corresponding to the communication link 81-1.
(e) Digital trunks (DTs) 77B-11 to 77B-1n that are directly connected to the respective digital links 71-11 to 71-1n and are connected to ones, of the ports of the switch module 75-1, corresponding to the respective digital links 71-11 to 71-1n. 
Since the submodules 74-2 to 74-N have the same configuration as the submodule 74-1, they are not illustrated in detail in FIG. 17 and will not be described. The components of the submodules 74-2 to 74-N will be given the same reference symbols as the corresponding components of the submodule 74-1 except that the reference symbols will have first suffixes xe2x80x9c2xe2x80x9d to xe2x80x9cN.xe2x80x9d
In the mobile communication system having the above configuration, the home location register 80 has a database in which combinations of a subscriber number, an identifier, and a switch identification number MSCID (described below) are registered.
Unique subscriber numbers that are given to respective mobile stations (including the above-mentioned mobile station 92) each of which is located in one of the wireless zones 91-1 to 91-N.
Identifiers acquired for the respective mobile stations according to a predetermined channel control procedure and that indicate, among the wireless zones 91-1 to 91-N, wireless zones (hereinafter referred to as xe2x80x9cvisit-zonesxe2x80x9d) where the respective mobile stations actually exist.
Unique switch identification numbers MSCIDs given to mobile-service switch offices each of which is connected to the gateway switch office 60 via its outgoing lines and is to perform call set-up in cooperation with a radio base station that forms the visit-zone.
A scheme of location registration for updating the contents of the database and a procedure of channel control performed during the course of the location registration through cooperation among the individual sections are not important features of the invention and can be realized by using various known techniques, and hence they will not be described.
In the mobile-service switch office 70, the main processor 72 cooperates with the call processors 76-1 to 76-N according to predetermined procedures of call set-up and channel control in such a manner as to exchange messages with the call processors 76-1 to 76-N.
In the submodule 74-1, the call processor 76-1 has the initiative of setting and canceling a speech path to be formed in the switch module 75-1 according to the above-mentioned procedures of call set-up and channel control. Further, the call processor 76-1 forms, as fixed pseudo-speech paths, in the switch module 75-1, communication links (not shown) for exchange of messages between the call processor 76-1 and the digital trunks 77G-1, 77H-1, and 77B-11 to 77B-1n. 
The digital trunks 77G-1, 77H-1, and 77B-11 to 77B-1n relay the following messages:
A message to be exchanged with the gateway switch office 60 via the inter-office link 61-1.
A message to be exchanged with the home location register 80 via the communication link 81-1.
A message to be exchanged with the radio base station 90-1 via the digital links 77-11 to 77-1n. 
Operations of the individual sections of the submodules 74-2 to 74-N are the same as those of the individual sections of the submodule 74-1 and hence will not be described.
When recognizing a call that has been forwarded to the local station via an incoming line (not shown) (indicated by symbol (1) in FIG. 18), the gateway switch office 60 judges whether the destination party is a mobile station that can be located in any of the wireless zones 91-1 to 91-N by performing code translation on the call (step (1) in FIG. 19). When the judgment result is true, the gateway switch office 60 acquires a subscriber number ID of this mobile station (for the sake of simplicity, it is assumed to be the mobile station 92) (step (2) in FIG. 19).
Then, the gateway switch office 60 generates a location request including the subscriber number ID and sends the generated location request to the home location register 80 via the communication link 62 (indicated by symbol (2) in FIG. 18; step (3) in FIG. 19).
The home location register 80 acquires, from the above-mentioned database, a visit-zone identifier (hereinafter referred to simply as xe2x80x9clocation informationxe2x80x9d) and a switch identification number MSCID that constitutes the combination (mentioned above) together with the subscriber number ID included in the location request (indicated by symbol (3) in FIG. 18; step (1) in FIG. 20).
Then, the home location register 80 sends a routing request including the subscriber number ID and the location information to the mobile-service switch office (for simplicity, it is assumed to be the mobile-service switch office 70) that is indicated by the switch identification number MSCID (indicated by symbol (4) in FIG. 18).
Among the communication links 81-1 to 81-N, a communication link to be used for the transmission of the routing request is selected through cooperation between an operating system and a driver (BIOS) (described below) or with a lead by one of those among pieces of software that are provided in the home location register 80.
An operating system provided as software higher in rank than an application system that gives a trigger for a routing request and performing a predetermined communication control.
A driver (BIOS) that performs physical interfacing with the communication links 81-1 to 81-N under the above operating system.
Therefore, when the above-mentioned routing request is sent from the home location register 80 to the communication link 81-4, for example, in the mobile-service switch office 70 it is transmitted to the call processor 76-4 via the digital trunk 77H-4 and the switch module 75-4.
Upon recognition of the routing request, the call processor 76-4 judges whether termination is possible at the mobile station 92 indicated by the subscriber number ID by recognizing a state and information described below based on the subscriber number ID and the location information included in the routing request (indicated by symbol (5) in FIG. 18).
A state that a certain call occurred in advance at the mobile station 92 indicated by the subscriber number ID and it still continues to exist.
Whether or not there is a factor (e.g., a subscriber class or subscriber data) that prevents the mobile station 92 from responding to paging of the local station.
Whether or not there is a factor (e.g., congestion or a trouble in the radio base station) that prevents paging of the mobile station 92 in the wireless zone (for simplicity, it is assumed to be the wireless zone 91-3) indicated by the location information.
A procedure of processing to be performed by the call processor 76-4 singly or in cooperation with the main processor 72 to recognize a state and information described above does not relate to the invention and can be realized by using various known techniques, and hence it will not be described.
When the judgment result is true, the call processor 76-4 assigns unique call identification information TLDN to the termination call concerned, generates a routing response including, together with the call identification information TLDN, the above-mentioned subscriber number ID and location information, and sends the generated routing response to the home location register 80 via switch module 75-4, the digital trunk 77H-4 and the communication link 81-4 (indicated by symbol (6) in FIG. 18; step (1) in FIG. 21).
Upon recognition of the routing response, the home location register 80 generates a location request response including the call identification information TLDN, the subscriber number ID, and the location information that are included in the routing response (indicated by symbol (7) in FIG. 18) and sends the generated location request response to the gateway switch office 60 via the communication link 62 (indicated by symbol (8) in FIG. 18; step (2) in FIG. 20).
Upon recognition of the location request response, the gateway switch office 60 generates an address message including the call identification information TLDN, the subscriber number ID, and the location information that are included in the location request response (indicated by symbol (9) in FIG. 18) and sends the generated address message to the mobile-service switch office 70 via one of the inter-office links 61-1 to 61-N (indicated by symbol (10) in FIG. 18; step
In the mobile-service switch office 70, when the address message has been sent from the gateway switch office 60 via, for example, the inter-office link 61-1, the call processor 76-1 accepts the address message that is received via the digital trunk 77G-1 and the switch module 75-1 (indicated by symbol (11) in FIG. 18).
The call processor 76-1 judges whether the wireless zone that is indicated by the location information included in the address message is the wireless zone that is formed under the call processor 76-1 itself (indicated by symbol (12) in FIG. 18; step (2) in FIG. 21).
When the judgment result is true, the call processor 76-1 acquires the call identification information TLDN and the subscriber number ID that are included in the address message concerned together with the location information and pages the mobile station 92 indicated by the subscriber number. ID by cooperating with the radio base stations 90-1 to 90-N via the digital trunks 77B-11 to 77B-1n and the digital links 71-11 to 71-1n (indicated by step (3) in FIG. 21).
However, when the result of the above judgment is false, the call processor 76-1 inquires of the other call processors 76-2 to 76-N, via the communication link 73 and the main processor 72, whether the wireless zone indicated by the location information that is included in the address message is the wireless zone formed under each of those call processors 76-2 to 76-N (indicated by symbol (13) in FIG. 18; step (4) in FIG. 21).
Upon,recognition of a call processor (for simplicity, it is assumed to be the call processor 76-3) with which an affirmative response has been obtained for the above inquiry among the call processors 76-2 to 76-N, the call processor 76-1 passes the above-mentioned call identification information TLDN and subscriber number ID to the call processor 76-3 and thereby transfers the leadership of the call processing and the channel control that relate to the termination call concerned (indicated by symbol (14) in FIG. 18; step (5) in FIG. 21).
Irrespective of the call processor (one of the call processors 76-1 to 76-N) that leads such a channel control and call processing, processing that is performed through cooperation among the individual sections to make the termination call concerned complete does not relate to the invention and can be realized by using various known techniques, and hence it will not be described.
Additionally, in the above conventional example, even when mobile stations to be termination parties are in the same visit-zone, in the mobile-service switch office 70 call processors to receive routing requests or address messages are not necessarily the same call processor and it is highly probable that they are different from call processors to lead call set-up and a channel control for termination calls concerned.
Therefore, in the process of such call set-up, the call processors 76-1 to 76-N need to share office data including subscriber data or cooperate with each other by exchanging desired messages with a lead by the main processor 72.
However, the sharing of office data and the exchange of messages require more resources such as memory blocks and throughput as the rate of interprocessor communications that are necessary to secure a desired response speed and service quality increases.
The necessary amount of such resources increases as the number of call that may occur parallel in accommodated mobile stations increases, resulting in increasing the running cost. Further, the necessary amount of such resources is the main factor of determining a traffic volume range where occurrence of congestion and an overloaded state is allowable.
An object of the invention is to provide a mobile-service switch, a home memory node, and a gateway switch capable of increasing efficiency of call processing and channel control without altering a basic hardware configuration and lowering service quality.
Another object of the invention is to flexibly adapt to various forms of functional distribution of a mobile-service switch office, a gateway switch office and a home location register and improve service quality at low cost in a mobile communication system applied to the invention without lowering high reliability to be attained by individual mobile-service switch offices performing call processing as distributed processing based on a load distribution scheme.
Another object of the invention is to reliably determine a means which is to perform call set-up to make a call occurring complete during the course of transit switching performed by a home location register in liaison with a gateway switch office or the gateway switch office alone so as to simplify and expedite processing relating to the call set-up.
Another object of the invention is to simplify a procedure of call processing, reduce the throughput of the call processing, and enable flexible adaptation to various forms of load distribution for the call processing.
Another object of the invention is to increase the completion rate of calls to be terminated at a mobile station.
Still another object of the invention is to simplify processing to be performed by a plurality of means to perform paging, compared with processing of notifying a judgement result of paging performed by a means other than the plurality of means.
Yet another object of the invention is to reduce a load of call set-up without substantially decreasing a call completion rate, compared with a case where a possibility of termination to a mobile station as a destination party is judged under the initiative of a switch other than a home location register.
A further object of the invention is to reduce a load of call set-up without substantially decreasing a call completion rate even when call processing in conformity with channel control over individual wireless zones is performed as distributed processing by a plurality of means.
Another object of the invention is to prevent unnecessary call processing in mobile-service switch offices other than the one which is to perform call processing in conformity with channel control over a wireless zone where a mobile station as a destination party can be located compared with a case where location information and the identifier of a call are notified in parallel to other mobile-service switch offices.
Another object of the invention is to realize flexible adaptation to various forms of load distribution of mobile-service switch offices while suppressing an increase in a load shared with submodules.
Another object of the invention is to prevent unnecessary call processing from being performed in parallel in submodules provided for load distribution in individual mobile-service switch offices.
Still another object of the invention is to suppress an increase in a load of mobile-service switch offices and realize flexible adaptation to various forms of load distribution even in a case where the load of individual mobile-service switch offices is shared with a plurality of submodules.
Yet another object of the invention is to realize flexible adaptation to not only forms of load distribution applied to individual mobile-service switch offices but also various forms of service.
A further object of the invention is to effectively utilize location information acquired during the course of location registration and achieve reduction of resources used for call processing and improvement of service quality.
The above objects are achieved by a mobile-service switch which judges whether or not termination is possible at a mobile station as a destination party in response to an inquiry from a home location register, determines a call processor (CPR) that is to perform a channel control over a wireless zone where the mobile station visits when the judgment result is true, and sends a response including identification information of the CPR to the home location register.
In the mobile-service switch having the above configuration, it is possible to determine a means for performing call set-up on a call which is to be terminated at any mobile station, judge a possibility of termination of the call, and notify the home location register or the gateway switch office of the result.
The above objects are also achieved by a mobile-service switch different from the above first mobile-service switch in that a response sent to the home location register does not include identification information of the CPR.
In the mobile-service switch having the above configuration, whereas the home location register is notified of the judgment result of a possibility of termination above, neither determined is a distributed call processing section that is to perform call set-up on the call concerned nor performed is processing of notifying the home location register of the determined distributed call processing section.
The above objects are achieved by a mobile-service switch which pages a mobile station as a destination party in subordinate wireless zones, determines, among those wireless zones, a CPR which is to perform a channel control of a base station having a wireless zone where a response has been obtained, and send a response including identification information of the determined CPR to the home location register.
In the mobile-service switch having the above configuration, a means to perform call processing on the above call is able to perform call set-up in a wireless zone where a mobile station to be a destination party is located as long as the mobile station wait in readiness for actually responding to paging.
In addition, the above objects are achieved by a mobile-service switch which performs paging in response to a request from another CPR and sends a response including identification information of a CPR which recognizes the response to the paging, to a home location register.
In the mobile-service switch having the above configuration, processing of notifying a result of the paging performed in parallel by a plurality of means is not performed by any of those means.
The above objects are further achieved by a mobile-service switch which judges, in response to an inquiry from a home location register including an identifier of a wireless zone where a mobile station as a destination party can be located, whether or not termination is possible at the mobile station, determines a CPR that is to perform a channel control over a wireless zone corresponding to the identifier when the judgment result is true, and sends a notice including identification information of the CPR to the home location register.
In the mobile-service switch having the above configuration, a wireless zone to be judged for the possibility of termination is determined under the initiative of the home location register having, as database, location information of a mobile station as a destination party.
The above objects are achieved by a mobile-service switch which judges, in response to an inquiry from a home location register including an identifier of a CPR that is to perform a channel control over a wireless zone where a mobile station as a destination party can be located, whether or not termination is possible at the mobile station and sends a notice including identification information of the CPR to the home location register when the judgment result is true.
In the mobile-service switch having the above configuration, the possibility of termination is judged based on a procedure of call processing by a means which is to perform call processing in conformity with channel control over a wireless zone where a mobile station to be a destination party can be located.
According to another aspect of the invention, there is provided a home memory node which has visit-zones of individual mobile stations as database and which, when receiving a location request from a gateway switch, notifies an identifier of a visit-zone of a mobile station indicated by the location request to a mobile-service switch which is to perform processing relating to a base station having a visit-zone of a mobile station.
In the home memory node having the above configuration, the above-mentioned location information and identifier are notified to a mobile-service switch office which is to perform call processing in conformity with channel control over the wireless zone where a mobile station as a destination party of a call is located.
The above objects are achieved by a home memory node which has, as database, identification information of a CPR to perform call processing in liaison with a channel control relating to individual wireless zones, temporarily stores a visit-zone included in a routing request at the time of sending the routing request. When a response indicating a possibility of termination at a mobile station corresponding to a visit-zone is received from a mobile-service switch office which is a destination of the routing request, the home memory node acquires identification information of a CPR corresponding to the stored visit-zone corresponding to the mobile station and sends the acquired identification information and the response to a gateway switch office.
In the home memory node having the above configuration, both of the identification information and the response are used for transit switching to be performed by the gateway switch office and the former is reliably notified to the gateway switch office even when it is not returned from any of the mobile-service switch offices.
The invention provides a home memory node which has visit-zones of individual mobile stations as database and sends a routing request including identification information of a CPR that is to perform processing relating to a base station having a visit-zone of a mobile station indicated by the location request, to a mobile-service switch office that is to perform the above processing when receiving a location request from a gateway switch office.
In the home memory node having the above configuration, the location information and the identifier of the call are notified to a specific submodule which shares a load of call processing among submodules provided in a mobile-service switch office which is to perform call processing in conformity with channel control over the wireless zone where the mobile station as a destination party of the call is located.
The invention provides a home memory node which has, as database, identification information of a CPR to perform call processing in liaison with a channel control relating to individual wireless zones and temporarily stores identification information of a CPR included in a routing request at the time of sending the routing request. When a response indicating a possibility of termination at a mobile station corresponding to the identification information is received from a mobile-service switch office which is a destination of the routing request, the home memory node acquires identification information of a CPR corresponding to the stored identification information corresponding to the mobile station and sends the acquired identification information and the response to a gateway switch office.
In the home memory node having the above configuration, both of the location information and the response are used for transit switching to be performed by the gateway switch office and the former is reliably notified to the gateway switch office even when it is not returned from any of the mobile-service switch offices.
The invention provides a home memory node which adds an attribute of a corresponding mobile station to a response to be sent to a gateway switch office.
In the home memory node having the above configuration, since the attribute indicates a form of service to be provided to the mobile station where a call has been terminated, the gateway switch office can perform transit switching for the termination call flexibly adapting to not only forms of load distribution applied to mobile-service switch offices but also various forms of service.
According to a further aspect of the invention, there is provided a gateway switch which requests location information of a mobile station to be a destination party of a call which has occurred from a home location register and when receiving from the home location register a routing response including identification information of a CPR that is to perform call processing on the call, requests the CPR indicated by the identification information to perform termination processing.
In the gateway switch having the above configuration, since an outgoing line used for transferring the call is determined under the initiative of a home memory, for a mobile-service switch office that is to perform call set-up relating to a destination party of the call, location information acquired during the course of location registration is effectively utilized, resources used for call processing is reduced, and the service quality is improved.
The invention provides a gateway switch which judges whether or not an attribute of a mobile station as a destination party that has been supplied via an incoming line or from a home location register satisfies a predetermined condition, and which requests a CPR indicated by identification information included in a routing response to perform termination processing only when the judgment result is true.
In the gateway switch having the above configuration, the attribute indicates a form of service to be provided to the mobile station where a call has been terminated so that it is possible to perform transit switching for the call with flexible adaptation to not only forms of load distribution applied to mobile-service switch offices but also various forms of service.